Since bitcoins (
http://www.bitcoin.org) are perfect for micro payments (almost nil transaction cost) they are perfect for helping a forum owner monetize his site. While a few users are willing to make $20+ donations through PayPal, enabling bitcoin donations opens up the world of $0.05 and $0.10 donations or even rewarding of posters by other users.
*Note, bitcoin.org is not related to bitcoin.com. It's bitcoin.org I'm talking about.